DPP tracks the changes to the RAW file in the original RAW file. that is ideal.
No extra XML file created in the directory as with Photoshop.

Aperture & LR4 tracks edits to the RAW file in the database. If that database is lost all your edits are as well. You have to start over. Deleting files is a hassle. You have one copy in the database and another where the original RAW files are. Performance in LR & Aperture can be very slow if you load a large RAW collection.

Yeah, newer version of Aperture & LR are better but I found that to be a hassle.
DPP still gives the best RAW conversions so I use it.